This family contains the Tropic-birds, similar in general appearance to large Terns but in structure closely allied to the Gannets, Cormorants and Private-birds. The plumage is principally black and white in the adults.
The bill is rather short, pointed, with no hook and with small narrow nostrils which are pervious ; the palate is desmognathous, the maxillo-palatines being separate behind, though united with the nasal septum anteriorly, whilst the vomer is well developed and conspicuous; the cervical vertebrae number fifteen; the femoro-caudal, semi-tendinosus and accessory semi-tendiuosus are present, the last-named muscle not occurring in any other of the Stegano-podous birds; the ambiens is absent; syringeal muscles are present.
The members of this family lay eggs which are extraordinarily like those of the Raptores, especially the genus Neophron of the Aegypiidae.
A great many genera have been created for this family but I retain all our Indian species in the one genus, Phaethon.